Sons whose mothers experienced high levels of stress during their first 18 weeks of pregnancy may have reduced fertility when they become adults.
The study, published in the journal Human Reproduction, evaluated the reproductive health of a cohort 643 of men at age 20, over half of whom had mothers that had experienced a stressful event within the first 18 weeks of their pregnancy, such as the death of a relative or friend, relationship problems, divorce, job loss or financial issues.
On average, those sons whose mothers were exposed to three or more stresses during early pregnancy had a 36 percent lower sperm count, 12 percent lower sperm motility and 11 percent lower blood testosterone levels than men whose mothers had not been under stress.
'This suggests that maternal exposure to stressful life events during early pregnancy, a vulnerable period for the development of male reproductive organs, may have important life-long adverse effects on men's fertility,' Professor Roger Hart, professor of reproductive medicine at the University of Western Australia and senior author of the study, told the Telegraph.
The first eight to 14 weeks of gestation are considered to be critical for normal embryonic development. In keeping with this, the authors of the study noted that the association between maternal stress and reduced fertility in subsequent male offspring was not seen when stressful events occurred later than 18 weeks into pregnancy.
'Our findings suggest that improved support for women, both before and during pregnancy, but particularly during the first trimester, may improve the reproductive health of their male offspring,' said Professor Hart.
The authors noted that as an observational study, the work was able to identify a correlation between maternal stress and reduced fertility in male offspring, but the underlying biological mechanisms responsible for this association remain unknown.
Professor Hart was also eager to urge prospective mothers to consider other risk factors that could affect the health of their children, such as smoking while pregnant. 'To provide some perspective, the association between exposure to stressful life events and reduction in sperm counts was not as strong as the association between maternal smoking and subsequent sperm counts, as this was associated with a 50 percent reduction in sperm number.'